All my Apple Blossoms are fragrant and some of my vittatum hybrids are fragrant too. Given its parentage, that particular cross could have a lovely fragrance in addition to its beautiful shape and coloration. I'm curious if that trait was passed on to your seedling. Have you detected any fragrance?

Xuan,H.Vittattum is one of the species which has some clones of other than diploid chromosome count. If you have a teraploid of that, you probably have a fertile tetraploid seedling. If it is diploid the chances are great that it is a triploid and mostly infertile.
Del